Spatio-temporal variation in recruitment on a seasonal, tropical rocky shore: The importance of local versus non-local processes

Abstract

The impacts of grazing and recruitment patterns on intertidal assemblage structure were examined on a semi-exposed rocky shore in Hong Kong. Recruitment was monitored in plots arranged in 3 different sites on the shore, in which fence treatments were used to manipulate grazer access. Plots were colonised by a variety of sessile invertebrates, erect and encrusting algae throughout the study period, with different species recruiting to sites 10s of metres apart during the same time period. Recruitment was highest during the winter with erect and encrusting algae colonising free space in all plots. While full fences around plots led to a higher percentage cover of algae, cover in partially fenced and open plots fluctuated at different times and between sites. Free space availability was greatest during summer, due to the seasonal die-off of species and negligible recruitment, as new species were unable to survive the extreme physical conditions during this period. The role of the local process of grazing, therefore, appeared to be of secondary importance in structuring assemblages on Hong Kong shores compared to non-local processes such as recruit supply and seasonal variation in physical stress.